Implement sort_workspaces() function for outputs.

This seems to have resolved issue #669 for me.

include/output.h

@@ -16,4 +16,7 @@ void get_absolute_position(swayc_t *container, struct wlc_point *point);
 // given wlc_point.
 void get_absolute_center_position(swayc_t *container, struct wlc_point *point);
 
+int sort_workspace_cmp_qsort(const void *a, const void *b);
+void sort_workspaces(swayc_t *output);
+
 #endif

sway/container.c

@@ -13,6 +13,7 @@
 #include "input_state.h"
 #include "log.h"
 #include "ipc-server.h"
+#include "output.h"
 
 #define ASSERT_NONNULL(PTR) \
 	sway_assert (PTR, #PTR "must be non-null")
@@ -180,24 +181,9 @@ swayc_t *new_workspace(swayc_t *output, const char *name) {
 	workspace->visible = false;
 	workspace->floating = create_list();
 
-	if (isdigit(workspace->name[0])) {
-		// find position for numbered workspace
-		// order: ascending numbers, insert before same number
-		//        numbers before unnumbered
-		int num = strtol(workspace->name, NULL, 10);
-		int i;
-		for (i = 0; i < output->children->length; ++i) {
-			char *name = ((swayc_t *)output->children->items[i])->name;
-			if (!isdigit(name[0]) || num <= strtol(name, NULL, 10)) {
-				break;
-			}
-		}
-		insert_child(output, workspace, i);
+	add_child(output, workspace);
+	sort_workspaces(output);
 
-	} else {
-		// append new unnumbered to the end
-		add_child(output, workspace);
-	}
 	return workspace;
 }
 
@@ -353,6 +339,7 @@ swayc_t *destroy_output(swayc_t *output) {
 				remove_child(child);
 				add_child(root_container.children->items[p], child);
 			}
+			sort_workspaces(root_container.children->items[p]);
 			update_visibility(root_container.children->items[p]);
 			arrange_windows(root_container.children->items[p], -1, -1);
 		}

sway/output.c

@@ -1,4 +1,6 @@
 #include <strings.h>
+#include <ctype.h>
+#include <stdlib.h>
 #include "output.h"
 #include "log.h"
 
@@ -177,3 +179,27 @@ void get_absolute_center_position(swayc_t *container, struct wlc_point *point) {
 	point->x += container->width/2;
 	point->y += container->height/2;
 }
+
+int sort_workspace_cmp_qsort(const void *_a, const void *_b) {
+	swayc_t *a = *(void **)_a;
+	swayc_t *b = *(void **)_b;
+	int retval = 0;
+
+	if (isdigit(a->name[0]) && isdigit(b->name[0])) {
+		int a_num = strtol(a->name, NULL, 10);
+		int b_num = strtol(b->name, NULL, 10);
+		retval = (a_num < b_num) ? -1 : (a_num > b_num);
+	} else if (isdigit(a->name[0])) {
+		retval = -1;
+	} else if (isdigit(b->name[0])) {
+		retval = 1;
+	} else {
+		retval = strcmp(a->name, b->name);
+	}
+
+	return retval;
+}
+
+void sort_workspaces(swayc_t *output) {
+	list_qsort(output->children, sort_workspace_cmp_qsort);
+}